With conventional automatic transmission controllers such as disclosed in Japanese unexamined patent publication No. 3-209048 for example, the torque input to the automatic transmission is estimated from the air intake flow rate (referred to hereunder simply as flow rate) and the rotational speed of the engine. The operating oil pressure or other control element for the automatic transmission is then controlled on the basis of this estimated torque.
When the engine torque TQSEN is computed in this way using a flow rate Qa and an engine rotational speed Ne, then the torque consumed by the engine itself must be deducted.
In the controller of the above-mentioned publication, this is dealt with by determining a flow rate friction component Qfric based on the engine rotational speed Ne. The engine torque TQSEN is then obtained using the following equation, where K is a constant: EQU TQSEN=K.times.(Qa-Qfric)/Ne
A problem arises however in that while the flow rate friction component Qfric can be determined at warm-up as shown in FIG. 9, from engine rotational speed Ne, additional temperature information is necessary for accurate determination at cool down.
The ideal temperature information in this respect is engine oil temperature. However since engine oil temperature is not used in other controls, this requires an extra sensor, thereby incurring additional costs.
Engine water temperature, oil (ATM) temperature and the like have been considered as possible alternatives. There are cases however wherein a rise in these temperatures does not show the same trend as that for engine oil temperature, so that they are somewhat lacking in accuracy as alternatives.
It is an object of the present invention, to address the above situation wherein the torque input to an automatic transmission is estimated using a flow rate corrected after eliminating a flow rate friction component, and be able to accurately correct the flow rate at the time of cool down without providing an additional sensor.